Simian virus 40 (SV40) encodes a 64 to 65 nucleotide RNA between nucleotides 2760 and 2825 on the L-DNA strand of the viral genome. This RNA, the SV40 associated small-RNA (SAS-RNA), is found in abundance late in the lytic cycle and appears to be specifically processed from large late RNA transcripts. The SAS-RNA is not detected in transformed cells. We are presently working to determine the function of this RNA. Sequence analyses demonstrates partial homology between the SAS-RNA and sequence near the viral orgin of replication. This indiates a possible function in replication or transcription. Direct hybrid selection of the SAS-RNA has shown that several other small RNAs are specifically selected. Some are specific to lytically infected cells while others are found only in transformed cells. We are presently mapping and sequencing these RNAs; this information will help in the design of experiments which will determine their functions.